The effects of crude extracts and an isolated compound from the leaves of milkweed, Pergularia daemia (Forssk) Choiv., on the antifeedant activity against two important lepidopteran pests, Helicoverpa armigera (Hub.) and Spodoptera litura (F.), were studied. Maximum antifeedant activity was recorded in ethyl acetate crude extract against H. armigera (70.3%) and S. litura (71.82%) at 1% concentration. Ethyl acetate crude extract was further subjected to column chromatography, which was performed using hexane as initial solvent and then by increasing the polar strength using ethyl acetate. Fractions collected at hexane and ethyl acetate (80:20) yielded 6-(4,7-hydroxy-heptyl) quinone, a novel compound which showed significant antifeedant activity against H. armigera (80.22% at 2000 ppm) and S. litura (68.31% at 2000 ppm).

Objective:The prime objective of this study is to evaluate the larvicidal and enzyme inhibitory effects of Acalypha fruticosa and Catharanthus roseus leaf extracts against Culex quinquefasciatus. Methods:Insecticidal susceptibility tests were carried out using the World Health Organization standard method, and the mortality was observed after 24 hrs exposure. Results:The tested extracts showed a significant larvicidal activity depending on the dose of the plant extracts. However, maximum larval mortality was detected in ethyl acetate extract of A. fruticosa with a lethal concentration (LC 50 ) value of 253.08 ppm and (LC 90 ) value of 455.40 ppm followed by hexane extract of C. roseus with LC 50 value of 645.33 ppm and LC 90 value of 1452.88 ppm against the larvae of C. quinquefasciatus. In control, there were five different fractions of α-carboxylesterases resolved in the gel with the mobilities ranging between 0.14 and 0.66. β-carboxylesterase isozyme profile of larvae treated with hexane extract of A. fruticosa showed higher enzyme activities by way of intense staining of fractions both at 1/4 and 1/10 LC 50 value of 48 hrs treatments. A. fruticosa ethyl acetate extract, and C. roseus hexane extract exposed larvae indicated increased quantities of β-Est4/5 isozymes in the concentration of 1/4 and 1/10 of LC 50 value of 24 hrs treatment when compared to control. The protein quantity in the majority of treatments decreased compared to control. Conclusion:The results revealed that the organic leaf extract of A. fruticosa and C. roseus had significant larvicidal and enzyme inhibitory effects against C. quinquefasciatus.

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